class_docstr: Test cases for "small data" conversion and I/O.
code: def test_to_html(self):
      expected = self.strip_all_whitespace(
          """
              <table border="1" class="dataframe">
                <thead>
                  <tr style="text-align: right;"><th></th><th>a</th><th>b</th></tr>
                </thead>
                <tbody>
                  <tr><th>0</th><td>1</td><td>4</td></tr>
                  <tr><th>1</th><td>2</td><td>5</td></tr>
                  <tr><th>3</th><td>3</td><td>6</td></tr>
                </tbody>
              </table>
              """
      )
      got = self.strip_all_whitespace(self.psdf.to_html())
      self.assert_eq(got, expected)
  
      # with max_rows set
      expected = self.strip_all_whitespace(
          """
              <table border="1" class="dataframe">
                <thead>
                  <tr style="text-align: right;"><th></th><th>a</th><th>b</th></tr>
                </thead>
                <tbody>
                  <tr><th>0</th><td>1</td><td>4</td></tr>
                  <tr><th>1</th><td>2</td><td>5</td></tr>
                </tbody>
              </table>
              """
      )
      got = self.strip_all_whitespace(self.psdf.to_html(max_rows=2))
      self.assert_eq(got, expected)
  
imports: import os
  import string
  import unittest
  import sys
  import numpy
  import pandas
  from pyspark import pandas
  from pyspark.testing.pandasutils import PandasOnSparkTestCase, TestUtils
  from pyspark.testing.sqlutils import SQLTestUtils
label_desc: Use image node_id 4 for calling the DataFrameConversionMixin obj's underlying member method code with example usage: obj.test_to_html() without return types